Electronic equipment is customarily cooled using rotary fans or blowers, which circulate air through the entire housing to maintain a constant operating temperature. Steady state temperature maintenance of the electronic components is important not only to prevent overheating, but also to assure reliable operation.
Most electronic equipment now contains only solid state electronic components, such as miniaturized transistors and integrated circuits, and no longer utilizes vacuum tubes and other generally large heat producing components. The amount of cooling required to maintain stable operating temperatures has therefore been substantially reduced. Also, the cooling requirements have been localized, since only several very small components, typically mounted on printed circuit boards, actually require cooling. Thus, cooling of the entire cabinet is not required. Nevertheless, even though wasteful, electronic equipment has continued to be cooled in this manner, since neither rotary fans nor other cooling devices have successfully been miniaturized, and rotary fans, which have been substantially improved over the years, continue to offer the most reliable and efficient method of cooling. Comparatively, however, when used in solid state electronic equipment, rotary fans or blowers stand out as the largest, noisiest, and most short-lived part of the assembly, the only moving component, and the component which most severely limits environmental tolerance specifications.
Another form of blower, using the principle of a vibrating blade, has been proposed in the past. Austrian Pat. No. 167,983 to Anderle, and U.S. Pat. No. 4,063,826 to Riepe are typical of such designs. In the Riepe patent a flexible blade is driven magnetically to deflect from side to side. The blade bends back and forth about a node point. The flapping end of the blade to the outside of the node point is disposed in a pumping duct to pump liquid through the duct. In the Anderle patent, a flexible blade is fixedly mounted at the inlet end of a blower duct and driven magnetically from side to side. Theoretically, due to the few moving parts, blowers of these types are susceptible of miniaturization; as a practical matter, however, they are generally so inefficient that they are better suited for producing heat than for generating cooling air movement, with the result that none has found any significant commercial acceptance.